1. Field of the Invention
The present invention relates to a heater for resistance-heated furnaces in which material is simultaneously treated at high temperature, preferably a temperature above 1000.degree. C., and high pressure, preferably in a gaseous atmosphere with a pressure above 500 bar.
2. Prior Art
In furnaces for extremely high temperatures, ceramic constructions in heaters to support resistance elements do not withstand the stresses occurring. The tendency to crack is considerable and is caused both by temperature alterations and pressure changes during a work cycle. In furnaces for temperatures higher than about 1400.degree. C., therefore, a heater constructed entirely of metallic material is used. In one known design a heating section comprises two semi-circular, horizontally directed arcs at the upper part of the section, each arc being supported by three vertical conductors. Between these arcs and a ring arranged under the arcs are a number of vertical resistance elements. These may be either straight or bent in zig-zag shape. The ring may be suspended in these resistance elements. Current is conducted to an arc and flows through the resistance elements to the ring, and to the resistance elements which are connected to the other arc and through the supporting conductors, back to the equipment supplying the current. Because of the asymmetry of the arcs, for instance, and the asymmetrical positioning of their support members, it has proved difficult to control thermal movement. The deformation occurring may cause short-circuits and other undesirable effects.